It's the same old same old this one...
The way I see it is this.
Option 1: 2.5 motor, drop in pistons, td05/6 turbo. Great set up, pretty much going to be troublefree, 400/400 no probs, and value for money.
Option 2: 2.5 built motor, c/w rods, hone to fit pistons etc, GT30 based turbo. Awesome set up, but costs initially are greater, and so are the costs for a twin plate clutch, 6 speed/PPG 5 speed etc etc..
It's all down to the folding stuff I'm afraid.